Anatomical Variations of the Osseous Tentorium Cerebelli and Transverse Sinus Canal/Groove in Small-Breed Dogs: A Computed Tomographic Study

The osseous tentorium cerebelli attaches to the inner surface of the skull and separates the cerebrum from the cerebellum, thereby dividing the cranial cavity into the rostral and caudal cranial fossae. The transverse sinus canal/groove, located near the attachment margin of the tentorium cerebelli, houses the transverse venous sinus. During surgical procedures, it is essential to understand the anatomical position of the osseous tentorium cerebelli and transverse venous sinus using the surface structure of the skull as a landmark. This study compared the positional variation of the attachment site of the osseous tentorium cerebelli and transverse sinus canal/groove relative to the external landmarks of the skull, specifically the external occipital protuberance and nuchal crest in small dogs. We analysed computerised tomography data from 23 client-owned dogs of four small breeds without brain or skull lesions. Using sagittal plane images from computed tomography (CT), the osseous tentorium cerebelli deviation distance (OTCDD) and the transverse sinus canal or groove deviation distance (TSCGDD) from external landmarks were measured. Both OTCDD and TSCGDD exhibited interindividual variation. In the interbreed comparison, the OTCDD was significantly greater in Chihuahuas than in Toy Poodles and Miniature Dachshunds. A strong correlation was observed between OTCDD and TSCGDD. This study demonstrated both interindividual and interbreed diversity in the anatomical positioning of the osseous tentorium cerebelli and transverse sinus canal/groove. Nevertheless, these structures consistently maintained a close spatial relationship. The findings contribute to a more detailed anatomical understanding of the skull in small-breed dogs and may assist in optimising craniectomy procedures.